1. Field of the Invention
The present invention relates to a light-emitting diode used mainly as a light source and to a method for manufacturing the same.
2. Description of Related Art
Light-emitting diodes (hereinbelow referred to as LEDs) have advantages of long life and low power consumption due to high light-emitting efficiency and there are high expectations for their use as light sources. However, such LEDs have a problem in that the luminance is difficult to control, i.e., a desired luminance is difficult to obtain.
A surface-mount-type LED is composed of a light-emitting element mounted on a substrate and a resin-sealing the light-emitting element. To control luminance of the light emitted from such LEDs, a method has been proposed in which SiO2 is added to the resin. However, in order to reduce the brightness of the LEDs, a large amount of SiO2 must be added to the resin, and this can cause a problem in that the workability and the properties of the cured resin are adversely affected.
To improve the light-emitting efficiency of the LEDs, a method has been proposed in which a member composed of an inorganic material such as titanium dioxide is provided around the light-emitting element and serves as a light scattering layer (see, for example, Japanese Patent Application Laid-Open No. Hei 11-284234).
However, in the proposed method, the titanium dioxide is used for improving the light-emitting efficiency of the LEDs, but does not improve the uniformity of the luminance of the emitted light. Moreover, in the case where a plurality of the LEDs are used, a method for improving the uniformity of the overall luminance of the LEDs has not been proposed.
For example, in backlights for large liquid crystal displays of 30 inches or more or for lighting devices for interior illumination, the use of LEDs as light sources is desirable in terms of life and power consumption. However, since a plurality of point light sources are used in the light source device, it is difficult to improve the uniformity of the luminance of light emitted from a light-emitting surface of the light source device.
In order to solve this problem, a method has been proposed in which the shape of an LED housing of a light guide plate is specially designed (see, for example, Japanese Patent Application Laid-Open No. 2006-12763).
However, the proposed method is based on the premise that the luminances of the LEDs serving as light sources are the same. Therefore, unless the plurality of LEDs each have an equal luminance to one another, it is difficult to maintain uniformity of the overall luminance of the LEDs.